Total body fat mass was estimated in 25 women and 21 men from densitometry. All subjects were apparently healthy. Subcutaneous fat mass was calculated by measuring subcutaneous fat thickness at 12 sites using A-mode ultrasound. The proportion of fat situated subcutaneously (PFSS) was found to vary considerably between individuals (range 0·50–0·97 in the women, 0·40–0·97 in the men). Moreover, there was no relationship between subcutaneous and internal fat masses. More information is required on the variability of the PFSS, and the technique described may have a role to play in this field.